diff --git a/src/equations/compressible_euler_quasi_1d.jl b/src/equations/compressible_euler_quasi_1d.jl
index ab661b8b35d..0a543277ee4 100644
--- a/src/equations/compressible_euler_quasi_1d.jl
+++ b/src/equations/compressible_euler_quasi_1d.jl
@@ -145,58 +145,6 @@ as defined in [`initial_condition_convergence_test`](@ref).
     return SVector(du1, du2, du3, 0.0)
 end
 
-"""
-    boundary_condition_slip_wall(u_inner, orientation, direction, x, t,
-                                 surface_flux_function, equations::CompressibleEulerEquationsQuasi1D)
-Determine the boundary numerical surface flux for a slip wall condition.
-Imposes a zero normal velocity at the wall.
-Density is taken from the internal solution state and pressure is computed as an
-exact solution of a 1D Riemann problem. Further details about this boundary state
-are available in the paper:
-- J. J. W. van der Vegt and H. van der Ven (2002)
-  Slip flow boundary conditions in discontinuous Galerkin discretizations of
-  the Euler equations of gas dynamics
-  [PDF](https://reports.nlr.nl/bitstream/handle/10921/692/TP-2002-300.pdf?sequence=1)
-
-  Should be used together with [`TreeMesh`](@ref).
-"""
-@inline function boundary_condition_slip_wall(u_inner, orientation,
-                                              direction, x, t,
-                                              surface_flux_function,
-                                              equations::CompressibleEulerEquationsQuasi1D)
-    # compute the primitive variables
-    rho_local, v_normal, p_local, a_local = cons2prim(u_inner, equations)
-
-    if direction == 1 # flip sign of normal to make it outward pointing
-        v_normal *= -1
-    end
-
-    # Get the solution of the pressure Riemann problem
-    # See Section 6.3.3 of
-    # Eleuterio F. Toro (2009)
-    # Riemann Solvers and Numerical Methods for Fluid Dynamics: A Practical Introduction
-    # [DOI: 10.1007/b79761](https://doi.org/10.1007/b79761)
-    if v_normal <= 0.0
-        sound_speed = sqrt(equations.gamma * p_local / rho_local) # local sound speed
-        p_star = p_local *
-                 (1 + 0.5 * (equations.gamma - 1) * v_normal / sound_speed)^(2 *
-                                                                             equations.gamma *
-                                                                             equations.inv_gamma_minus_one)
-    else # v_normal > 0.0
-        A = 2 / ((equations.gamma + 1) * rho_local)
-        B = p_local * (equations.gamma - 1) / (equations.gamma + 1)
-        p_star = p_local +
-                 0.5 * v_normal / A *
-                 (v_normal + sqrt(v_normal^2 + 4 * A * (p_local + B)))
-    end
-
-    # For the slip wall we directly set the flux as the normal velocity is zero
-    return SVector(zero(eltype(u_inner)),
-                   p_star,
-                   zero(eltype(u_inner)),
-                   zero(eltype(u_inner)))
-end
-
 # Calculate 1D flux for a single point
 @inline function flux(u, orientation::Integer,
                       equations::CompressibleEulerEquationsQuasi1D)